It is known to provide a motor vehicle suitable for performing wading operations in water. For example, ‘off-road’ vehicles are known that are suitable for performing wading operations at depths of over 0.3 m and in some cases at least 1.0 m
The problem exists that a driver driving over uneven, submerged ground may experience difficulty in determining whether the level of water around the vehicle is below a prescribed water level limit of the vehicle.
Most on-road vehicles are capable of driving through shallow water, for example water of depth 150 mm or less as long as the vehicle speed is slow enough not to cause excessive splashing. Driving through water of a depth up to around 300 mm is often referred to as ‘fording’.
For road vehicles, the ride height (i.e. the height of the vehicle floor above ground) is typically lower than for off-road vehicles. Due to this relatively lower ride height a fording event for a road vehicle may pose similar risks of water affecting vehicle systems as a wading event for an off-road vehicle. As such, the use of the term wading in respect of the present invention may be considered to include any fording or wading event.
It is known to provide a wading apparatus to assist a driver in conducting a wading operation. The apparatus comprises multiple ultrasonic sensors that are mounted around the vehicle for determining a distance of the surface of water from the sensors during a wading operation. The signals from the sensors allow vehicle pitch and roll to be determined.
Use of ultrasonic sensors has the disadvantage that a settling time must be allowed after switching on the sensors before reliable distance information can be obtained by means of the sensors.